The situation is the same with a TL.
In a TL you have 2 sources to line up. In a tapped horn you have 3. A tapped horn is not damped give ng it the limited bandwidth.
Tapped horn is a creative, and original, use of a quarter-wave enclosure.
So it becomes a Big Vent Reflex?
dave
Not something i would use for HiFi. Too much resonance, and subsequent phase issues. Never got interested in them once i understood the compromises. And hear the bass in the KEF 104II.
dave
Last edited:
Okay -I'll make a one-off, as I'm having a self-imposed break from all forums due to some health and other issues. So I'm not going to be looking here again.
I'd love to know where these set-in-stone definitions that are being so strongly stated are coming from, because trying to impose highly rigid definitions on enclosures when those definitions themselves are not fixed or have significant overlap is an exercise in futility. 'Bass reflex' is a good example, since historically speaking, a bass reflex is a traditional pre-Novak, Thuras style enclosure, rather than vented types derived from Novak, Thiele, Small or other similar work, but it's still regularly used as a description. Ultimately they're all Helmholtz resonators, providing there is a uniform internal air particle density and no eigenmodes present to affect the alignment. The sub-level terminology is where you get differences, not physics.
Some generalities:
I'd love to know where these set-in-stone definitions that are being so strongly stated are coming from, because trying to impose highly rigid definitions on enclosures when those definitions themselves are not fixed or have significant overlap is an exercise in futility. 'Bass reflex' is a good example, since historically speaking, a bass reflex is a traditional pre-Novak, Thuras style enclosure, rather than vented types derived from Novak, Thiele, Small or other similar work, but it's still regularly used as a description. Ultimately they're all Helmholtz resonators, providing there is a uniform internal air particle density and no eigenmodes present to affect the alignment. The sub-level terminology is where you get differences, not physics.
Some generalities:
- A [single] tapped horn, if we use operating physics to define it, is simply a loose, non-specific term for an expanding pipe with the driver tapped into the expansion at a desired distance from the throat. That's it. End of.
- A DSL type tapped horn, enclosure, like the Jensen Transflex before it, is technically speaking double-tapped (and a horn if the pipe is expanding toward the terminus) since the driver excites the pipe at two physically separate locations. Also 'that's it, end of.' The definition is no more specific or detailed than that. IIRC, Tom himself has said in the past 'the ancients keep stealing all my best ideas'. They are (with some modified exceptions) strictly speaking the logical extreme of a 6th order BP alignment.
- A back loaded horn is an expanding pipe excited by the rear of the drive unit. Again, it's no more specifically defined than that, even if some might wish it (and many other things) to be. It might be better if it were, but as they say, 'wishing don't make it so'. Depending on the expansion rate, it may or may not be impedance matched down to the QW cut-off frequency; if the expansion is compromised compared to the optimum / ideal, once any designed boundary loading is factored in, then it relies on resonant action from that QW cut-off frequency up to the point it is impedance matched. That doesn't mean it isn't a horn, it's simply that the expansion is compromised vis-a-vis the length, almost invariably for practical reasons (which doesn't imply ignorance on the part of the designer either).
- Chambered back-horns can be described as extreme variations on the vented box -we're 'simply' (ha!) dealing with a situation where as the chamber shrinks, the vent enlarges & visa-versa. Simplistic, but gives a reasonable insight into operation & BW targets. These are not 'set in stone' definitions though, because as soon as you move beyond the underlying / operating physics, there generally aren't any ('transmission line' being the most notorious example)
- Most scoop bins are just very simple back [loaded] horns, in a large proportion of cases compromised in the same way as most other undersized back horns. Like any other back-loaded horn, they may or may not have a low-pass filter chamber (aka 'air cavity' -since with the exception of the handful of reactance-annulled back-loaded horns, the space they sit in is their compression chamber -which usually means zero compression for most practical purposes). There can be some crossover (pun intended) depending on the horn expansion & the size of the chamber itself, which in some designs doubles as the first expansion stage.
- You can find (and Olson set the precedent) horns with LP chokes inserted into the expansion path; the FH series are just a recent example.
- Front horns (loaded by the front of the driver) can be compromised in terms of their expansion just as back-loaded types can.
Yes, cause that's all a TL is...a BR with a fancy port.
I can agree that the position of the driver might be an issue when there is no compression chamber in a TL.
With the example below, I don't see where there would be major difference in performance between the 2 enclosures.
Mount the driver on the 2nd panel of each enclosure and there would be a HUGE difference in performance.
I bet you would not say that if you could put two 20hz FLH's in your listening area.
A BR by definition has no eigenmodes, a TL differs in that it does. Your statement is balderdash.
All that does is show that you do not have any idea what driver offset (Zd) brings to the party. This was a key finding by MJK in the early 2000s. It dramatically changed the landscape of TL design.
dave
With a 20 HZ FLH (if it stretches to 4 octaves, runs out of steam about 300 Hz) the horn usually is in the back yard, or under the floor. I had a customer with one of those.
And what does a bandpass box have to do with a proper size FLH?
dave
Look at 3 x Fb through 5x Fb. A miracle occurred 😀. 3x Fb is no longer resonating and 4x Fb is no longer a cancelation notch. instead you have bandwidth out to the 5 x Fb resonance and cancelation centered at 6 x Fb
Ok, you getting way too technical for me.
I totally understand driver offset. I've modeled plenty of OD functioned enclosures in HR. Most of the time, I can get the same response without using the OD function.
MOST of the time, the driver's position does not affect the response in a TL or BR enclosure. The driver's position is CRITICAL in modeling a TH, TH1, etc function enclosure in HR.
In SIMPLICITY, TL's and BR's are direct radiator enclosures with a port/vent/passive radiator.
TL's NORMALLY have positive and negative flare ports.
BR's NORMALLY have straight flare ports or passive radiators.
You can model a straight flare TL enclosure the exact same way you can model a BR enclosure HR.
I provided the link where someone built and measured a TL and then removed part of the line and the BR had a better response, however they were still the same enclosure externally and volume wise internally.
Tech people wonder why non tech people think tech people are nerds with stuff like "A BR by definition has no eigenmodes." K.I.S.S.
These all have 1/4 wave resonances based on the length from start to finish. So they are all ‘TL’ I suppose? (Even if the Fb is loosely based on helmholtz maths in the tapered and coupling chamber versions)??
Last edited:
I give up on Mr BandPass. He keeps making silly assumptions.
Seems to be where he is getting lost… he does not really understand the physics.
What is the frequency range of the QW boxes you build?
dave
Seems to be where he is getting lost… he does not really understand the physics.
What is the frequency range of the QW boxes you build?
dave
Tru. However, buried driver enclosures are not direct radiator enclosures. There is a difference.
There are small to little differences between a BR and TL, especially when modeling the Coupling Chamber version of a TL enclosure.